1. Field of the Invention
This invention concerns a lightweight portable carrier having a thermally insulated chamber which can be heated or cooled.
2. Description of the Prior Art
Food coolers of sufficiently light weight to be comfortably carried by a person are well known. Typically, such coolers are chambers of rigid box-like construction, fabricated of a closed cell polymeric foam such as polystyrene, and provided with a lid and carrying handle. Because of the thermally insulative nature of the foam, articles within the chamber, whether hot or cold by comparison with the temperature of the surrounding ambient air, will tend to remain at reasonably constant temperature for limited periods of time. To compensate for the limited heat transfer that does occur through the walls of the chamber, cooling means in the form of ice or a container of cold or frozen liquid may be located within the chamber to maintain low temperature. Similarly, heating means such as a container of hot liquid, or electrical heating means may be located within the chamber to maintain an elevated temperature.
Although such food-carrying containers are reasonably effective and inexpensive, they occupy considerable space, even when not in use. Furthermore, the traditionally employed cooling means generally occupies a considerable portion of the chamber, and is limited in its duration of effectiveness. For example, in an automobile trip of long duration, ice might not be obtainable at roadside locations to replenish ice which has melted in the cooling chamber. In addition to serving to preserve the freshness of food, the cooling chamber may be utilized preserve medications such as insulin, or to preserve photographic films.
Flexible thermally insulated carrying bags are disclosed in U.S. Pat. Nos. 4,671,393 and 5,005,679. Such carrying bags however, are generally of limited capacity, and usually do not provide adequate thermal insulation or cooling means for long duration periods.
Peltier thermal control devices are based upon the principle that, at the junction of two dissimilar materials through which an electric current passes, caloric heat is produced or absorbed, depending upon the direction of the current. The rate of the caloric effect is proportional to the magnitude of the current. By positioning a multitude of such junctions thermally parallel and electrically in series in a small space such as in a metal block, a significant caloric effect can be produced. Such devices now commercially available with junctions of p-type semiconductor materials in contact with n-type materials are operable on 12 volts direct current, and employ a polarity switch to change from heating to cooling modes. A fan is generally associated with the device to circulate air from the block to the objects or region where the thermal effect is desired.
It is accordingly an object of the present invention to provide a lightweight thermally insulated carrier having a Peltier thermal control device.
It is another object of this invention to provide a carrier as in the foregoing object which is easily compactable to a storage state of relatively small volume.
It is a further object of the present invention to provide a carrier of the aforesaid nature of simple, durable construction amenable to low cost manufacture.
These and other beneficial objects and advantages will be apparent from the following description.